The space programmes of the USA and USSR began in a spirit of bitter Cold War rivalry but by the early 1970s internation tensions had eased a little into a d†étente and what had been unthinkable ten years earlier was possible. In 1975 the world saw the historic meeting in orbit between astronauts and cosmonauts. This was the Apollo-Soyuz Test Project.
The two crews pose together on the ground with a model of their docked craft. Left to right, they are Slayton, Stafford, Brand, Leonov and Kubasov. (image credit: NASA)
From the time of the earliest spaceflights, people had imagined scenarios where humans could be stranded in crippled spacecraft demanding the launch of an urgent rescue mission. Such a mercy flight could take any nation weeks to organise and the stricken crew could in such peril that this would be too late. The human instinct is to help those in danger regards of nationality, creed or other division, so perhaps some other nation, even one normally considered hostile, could send one of its vessels to assist.
This cutaway artist’s impression shows the Apollo and Soyuz connected by the Docking Module. Two astronauts are transferring to the Soyuz. (Image credit: NASA)
By 1969 US and Soviet experts had discussed this scenario and saw that would be far easier said than done. For a start, American and Soviet spacecraft had independently developed docking mechanisms to allow two vessels to join and people to move between them but the two nations used utterly incompatible systems. They used completely different radio frequencies and procedures to perform the docking manoeuver. Perhaps docking the spacecraft together in a rescue mission was not necessary, could the stricken crew don spacesuits and abandon ship, spacewalking to clamber abroad the rescue vessel? Sadly even this would be impossible, US and Soviet spacecraft used completely different atmospheric pressures and mixtures of gases, moving from one nationòÀÙs craft to another could be horrifyingly dangerous. If in, say 1970, the crew of a Soyuz had been unable to return home, an Apollo CSM could have been brought alongside their craft, but the Apollo crew could only be unlookers to the unfolding tragedy, unable to offer material assistance.
This seemed a grotesque prospect and it inspired meetings to plan how to make lifesaving in space a possibility. In 1972 the two superpowers signed an Agreement on Co-operation in the Exploration and Use of Space for Peaceful Purposes which called for the technology for a successful docking to be developed and tested by 1975 and so the Apollo-Soyuz Test Project was born.
Technicians and astronauts from the US and USSR would plan how to overcome their mutual differences and demonstrate their success by a rendezvous between their spacecraft. The other major aspect of ASTP was political, to enhance trust between the Americans and Soviets and prove to the world that the two superpowers could cooperate despite their radically different visions of the human future. For NASA the project was helpful in providing a bridge between the era of Moon landings and Skylab and the beginning of Space Shuttle flights (expected in about 1978).
Engineers from both countries made remarkable progress despite the enormous language and cultural barriers. There were two large technical challenges in docking an Apollo CSM and a Soyuz. How could two docking mechanisms of different sizes, with incompatible latches come together and make a rigid and safe pressurised seal? Then if docking was successful there was the problem of the craftsòÀÙ atmospheres. Apollo NASA astronauts breathed pure oxygen at about one third normal atmospheric pressure while in a Soyuz the cosmonauts used a mix of nitrogen (66-78%) and oxygen (19-32%) maintained at half to two thirds the atmospheric pressure on EarthòÀÙs surface. A cosmonaut acclimatised to this atmosphere who then transferred in the ApolloòÀÙs environment would experience the agonising and debilitating condition known to deep-sea divers as the òÀÜbendsòÀÝ (or more properly, decompression sickness) as bubbles of nitrogen formed in his body fluids.
The vital ASTP Docking Module. This was built by Rockwell International who also was responsible for the Apollo CSM and Shuttle Orbiter. In the 1990s Rockwell was absorbed into Boeing. (Image credit: NASA)
The solution to both problems was to develop a specialised piece of hardware called the Docking Module (DM) which was manufactured by Rockwell International. Carried into space stowed under the Apollo CSM (just like a Lunar Module) on the same Saturn 1B rocket, the Apollo would dock with a compatible port on one end of the tubular DM, on the other end of the DM was a Soyuz-compatible port. Essentially the DM was an adaptor between the two spacecraft. Once the two ships were successfully joined, the DM would service as an acclimatisation chamber. Transferring between spaceships would not be quick and easy. To move from the Apollo to the Soyuz, astronauts would go into the DM and close the hatch behind them. The atmosphere in the DM would gradually increase in pressure and be enriched with nitrogen. When the pressures in the DM and Soyuz were equal, the hatch into the Soviet craft would be opened and the Apollo crew could meet their fellow space travellers face to face. This procedure was reversed for moving from the Soyuz to the Apollo.
The plan for the mission (Image credit: NASA)
The mission began on 15 July 1975 with the launch of Soyuz 17 which was the first Soviet launch to be televised live. On board the craft was its commander, veteran cosmonaut Alexei Leonov (b1934), the first man to make a spacewalk, and his flight engineer Valery Kubasov (1935-2014), a veteran of the Soyuz 6 mission. Both men had been intended to spend time on the Salyut 1 space station during the Soyuz 11 mission but had been grounded for medical reasons and taken off the flight. This inconvenience had saved their lives, their replacements on Soyuz 11 perished in a dreadful accident. As Soyuz 17 was being prepared for its mission,ˆà a complete backup Soyuz and launch vehicle were readied should Kubasov and Leonov fail to reach orbit. Happily this was not needed.
The Soyuz 19 spacecraft seen from the Apollo. These vehicles are normally dark greyish green all over. This was considered to make the Soyuz too dark to see against the blackness of space for NASA’s docking procedure. The white areas and several flashing beacon lights were added to Soyuz 19 especially for the ASTP to increase its visibility. (Image credit: NASA)
Seven and half hours later the Apollo (which, contrary to myth, was not designated Apollo 18) blasted off. This was both the last flight of an Apollo spacecraft and the final flight of a Saturn series rocket. The American crew was commanded by Thomas Stafford (b1930) who had orbited the Moon on Apollo 10. The Command Module Pilot was Vance Brand (b1931) who was making his first space flight but went on to command three Shuttle missions. The third Apollo crew member was the DM Pilot Donald òÀÜDekeòÀÝ Slayton (1924-93) , one of the original òÀÜMercury SevenòÀÝ astronauts. Slayton had been picked as an astronaut in 1959 but to his intense disappointment had been grounded for medical reasons throughout the Mercury, Gemini and Moon landing missions. By 1972 the heart murmur that had caused his grounding had cleared up and he was cleared to fly but this would be his only space flight. At the age of 51, he was at the time the oldest person to go into space.ˆà Also on board the Apollo was a very confused mosquito which had somehow been sealed in the Command Module (alas the insect stowaway failed to survive more than a few hours; perhaps the reduced pressure/pure oxygen atmosphere of the CSM was eventually fatal to it).
The ASTP crews (and their backups) had learned each othersòÀÙ languages and trained and socialised together in Moscow and Houston. All former fighter pilots, they had got on well together (especially surprising when you consider that their early military caree